Cold weather Chronograph results.

[Cold Trigger Finger]

As it turned cold again I was staying home today to keep the house warm. I figured it would be a good time to do a little Chronographing. I put the rifle and ammo outside for 45 minutes with the bolt open. I got the chrony ready and went out in the yard with chrony and rifle. Set chrony down, turned it on backed off 18' and commenced fire.
Temperature -40°f
Rifle, Ruger M77 Hawkeye Stainless
Cal. 6.5 Creedmoor
bullet, 110 gr Barnes Banded Solid moly tumbled
Powder, Varget. 39 grains
Primer CCI 200
1, 2931 . 2, 2931 . 3, 3007 . F. P. S .

I have chronographed this load at 40°f and got
1,3040
2, 3020
3. 3034 .
Same distance to chrony.
I didn't have any high pressure signs and I don't think I'm at Max.

 

[Tumbleweed]

It appears that you are experiencing powder temp sensitivity. I don't have experience with the powder you are using, but with 100fps difference between the 40 and -40 this is probably what you are running into.

 

[TX mountain hunter]

Interesting. Thanks for sharing the results, I've been curious about how much the temperature swing will affect muzzle velocities myself lately. I assume that the 3007 fps was either after the gun warmed up the powder a little or you had it in your pocket or something different? Seems like a bit of an outlier..

Your -40 comments are making me not dread +20 as much now (where I'll be heading in a couple weeks). I just thought I got cold around here when it starts dropping below 45 or so.

As it turned cold again I was staying home today to keep the house warm. I figured it would be a good time to do a little Chronographing. I put the rifle and ammo outside for 45 minutes with the bolt open. I got the chrony ready and went out in the yard with chrony and rifle. Set chrony down, turned it on backed off 18' and commenced fire.
Temperature -40°f
Rifle, Ruger M77 Hawkeye Stainless
Cal. 6.5 Creedmoor
bullet, 110 gr Barnes Banded Solid moly tumbled
Powder, Varget. 39 grains
Primer CCI 200
1, 2931 . 2, 2931 . 3, 3007 . F. P. S .

I have chronographed this load at 40°f and got
1,3040
2, 3020
3. 3034 .
Same distance to chrony.
I didn't have any high pressure signs and I don't think I'm at Max.

 

[Cold Trigger Finger]

Yes, the 3rd round was in the chamber for close to 1 minute. It took me a short time to check the chrony to make sure there was no error. Plus as it was in the bottom of the mag I think it hadn't got quite as cold as the 2 above it.
Some may think the 100 fps velocity drop is significant. And in some ways it is, but lots of other powders will loose 200-400 and more fps of velocity drop and will blow so much unburnt powder out the muzzle that a Chronograph will always show an error unless it is put ay 25-30 yards from the muzzle.
RL 15 is pretty bad in the cold (-20 and colder)
I've had hang fires with BLC2.
For me as a hunter, 2900 fps is still very useful velocity.
My goal is to record the real velocity drop so that I can figure the poi drop and wind drift. At the different temps.

And a guy told me that some of the custom barrel makers won't ship stainless barrels up here because they say they will shatter in the cold.

 

[Tumbleweed]

FWIW, this is the reason I switched to Hodgdon's extreme powders a few years ago. They are probably the most consistent powders when exposed to large temp swings like what you are talking about. I have been very pleased with H1000 and don't see myself changing powders again, very consistent.

 

[TX mountain hunter]

Are either of you familiar w IMR 4831 and how it handles extreme cold?

 

[Tumbleweed]

Are either of you familiar w IMR 4831 and how it handles extreme cold?

No, the only IMR powder I've used has been 7828SSC that I used in a friend's 300 Win. I have not tested the velocities at extreme temp changes.

 

[Cold Trigger Finger]

IMR 4831 is not advertised as being an extreme extruded.

 

[Cold Trigger Finger]

It is pretty easy for anyone to check their loads . And rifle. Put the ammo and rifle in your deep freezer for a couple hours, Set your chronograph up then grab the rifle and ammo and go chronograph it. That is provided you have your freezer real close to where you can shoot. Where I am I have to put the rifle and ammo outside but keep the chrony by the wood stove. , I get the rifle all set up then take the chrony outside, set it, turn it on and commence fire. At -40 I can get at least a 3 shot string before the chrony freezes up.

 

[FEENIX]

FWIW, this is the reason I switched to Hodgdon's extreme powders a few years ago. They are probably the most consistent powders when exposed to large temp swings like what you are talking about. I have been very pleased with H1000 and don't see myself changing powders again, very consistent.

Varget is one of the extreme powders.

Extreme Rifle Powders

 

[Tumbleweed]

Varget is one of the extreme powders.

Extreme Rifle Powders

Thanks for pointing that out Feenix! I didn't realize that was an extreme powder. I am surprised that the OP is having such high temp swings then

 

[FEENIX]

Thanks for pointing that out Feenix! I didn't realize that was an extreme powder. I am surprised that the OP is having such high temp swings then

Let's face it, -40 °F is beyond extreme cold, that's just flat out non-titillating cold.

IIRC, the test for the extreme powders were 0 to 125 °F (???).

 

[farout]

I heard somewhere that once you get to these sorts of low temps that a hotter primer might help. I believe Winchester makes the hottest primers. Would be interesting to see if a Winchester WLR or even a WLRM primer helped.

 

[Cold Trigger Finger]

Ya a hotter primer may help. And 40 below is cold
But it feels warm compared to 60 below which is real cold until it gets colder and starts blowing. As I type this it's 40 below at my house. And it really doesn't feel that cold. There are Lots of people who hunt up here in the cold.